Sentinel lymph nodes in malignant melanoma: Extended histopathologic evaluation improves diagnostic precision

Abrahamsen and colleagues recently reported that more extensive serial sectioning of sentinel lymph nodes (SNs) leads to an increased rate of detection of melanoma micrometastases.1 Although the authors acknowledged that SN analysis involves a compromise between 1) comprehensive sampling and examination of the entire lymph node and 2) practical and economic considerations in routine practice, they did not expound on this issue. We believe that it is important for pathologists and clinicians to understand the practical ramifications of adopting a protocol such as the one used by Abrahamsen et al.1 for routine histopathologic assessment of SNs. If an average time of 1 minute is required to screen each section (a conservative estimate in our experience), and if, on average, 20 sections of each paraffin block obtained from each SN are examined, then, based on median values (2 SNs per patient and 2 paraffin blocks per SN), a pathologist can examine no more than 6 cases in an 8-hour working day! At the Sydney Melanoma Unit (SMU; Royal Prince Alfred Hospital, Camperdown, Australia), we routinely examine four sections of each paraffin block obtained from each available SN; initially, these sections are screened using a 10X objective lens. In 2003, SNs obtained from a total of 434 patients with melanoma were examined, with the examination process consuming approximately 200 hours of pathologists' time. Adoption of the sectioning protocol described by Abrahamsen et al. would call for these pathologists to spend an extra 463 hours examining SNs each year. (Furthermore, additional time would be required for laboratory technicians to cut and stain these sections.) These changes would result in a prohibitive increase in the cost of histopathologic assessment of SNs. We recently reported on the extensive SN biopsy experience accumulated at the SMU.2 Between 1992 and 2001, 26 of 976 patients who had undergone SN biopsy for primary melanoma developed regional lymph node field recurrences after initial pathologic examination of the SNs in these fields yielded negative findings. On the basis of these results, we concluded that efforts to reduce this already very low rate by routinely examining additional sections would be difficult to justify from a cost-benefit perspective. In our view, it is important that practical and economic issues, as well as clinical outcomes, be considered in the development of protocols for detecting metastatic disease in SNs. It is clear that less labor-intensive methods for reliable detection are required, and as we recently reported, nonhistopathologic techniques such as magnetic resonance spectroscopy have the potential to fulfill this need.3